In general, an extrusion molding method is a one of metal processing methods of putting an extrusion material into a container and pushing the extrusion material using an extrusion nozzle of an extrusion die to manufacture a long product having a constant cross section, and as a material, aluminum having a low melting point, an aluminum alloy, or rubber has been mainly used.
Recently, the extrusion molding using the aluminum material or rubber material as described above has been applied to process a component such as a sash member, a vehicle body, a bumper, or the like, of a vehicle such as a passenger car, a truck, or the like, due to excellent durability and recyclability.
The extrusion molding method as described above may be roughly classified into a forward extrusion method and a backward extrusion method, wherein the forward extrusion method is an extrusion method when a direction of an extruded metal is the same as a direction of pressure applied from the outside, and the backward extrusion method is an extrusion method when the direction of the extruded metal is opposite to the direction of pressure applied from the outside.
In addition, extrusion performed at a high temperature is referred to as hot-extrusion, and extrusion performed at room temperature is referred to as cold-extrusion.
Among them, an extrusion molding method by forward extrusion method will be briefly described. A product having a desired cross-sectional shape may be extrusion-molded by fixing an extrusion die having an extrusion nozzle having a cross-sectional shape to be manufactured to a front end of a container and pressurizing an extrusion material toward the extrusion die by a pressurizer (main ram) to extrude the extrusion material in the extrusion nozzle simultaneously with inserting a heated extrusion material into the container.
That is, since the extrusion nozzle of the extrusion die has a constant cross-sectional shape, the product to be manufactured by extrusion may be molded so as to have a constant cross-sectional shape corresponding to the extrusion nozzle.
As described above, since the cross-sectional shape of the product is the same as the shape of the extrusion nozzle of the extrusion die, a round bar, an angular bar, a section member, a pipe, and other arbitrary products may be manufactured by suitably changing the shape of the extrusion nozzle of the extrusion die.
Meanwhile, at the time of extrusion processing, since there is a need to push the extrusion material made of a metal material or rubber material using the extrusion nozzle, a significantly large amount of force is required, such that tools capable of enduring high temperature and high pressure is required together with large scale mechanical equipment.
However, in the case of the product manufactured by the extrusion processing as described above, since the product has a constant cross-sectional shape and is formed to be long, it is difficult to produce a product of which a cross-sectional shape is variable such as a door frame for a vehicle.